In the production of glass containers by the press and blow method on the well known I S type machine, a gob of glass is provided to a blank or parison mold comprising two mold members or halves which are supported by a mold mechanism at a blank station of the machine, which mold members can be closed to form a mold cavity_ The glass in the mold cavity is pressed into the required shape of a parison by a plunger moving upwardly into the mold cavity, a lower portion of the glass being forced into a neck ring of the mold. The plunger is then withdrawn and the parison is carried by the neck ring away from the blank station and is transferred to a blow mold station where it is blown to the required shape. In the blow and blow method a gob of glass is provided to the parison mold and is then blown into the required shape of a parison. The shaped parison is again carried by a neckring away from the blank station to a blow mold station.
It is necessary to cool the parison mold and this is commonly done by providing the mold members with cooling passages extending axially therethrough from a lower end face to an upper end face of the mold member. Commonly, for reasons of space, the cooling air has been provided to the upper ends of these cooling passages, and has passed downwardly through the mold members, but this does impede access to the blank mold mechanism.
In I S machines as employed at present, the cooling applied to the two blank molds in a double gob machine does not differentiate between the two blank molds. This is in fact disadvantageous, as the two blank molds heat up to different extents and as a result the two parisons delivered to the blow molds are not in the same temperature condition as each other, which can lead to the formation of unsatisfactory containers.
GB 2151608 describes an arrangement for cooling the blank mold members at the blank station of a double gob IS machine in which air is supplied to a plenum chamber which is positioned over the upper portion of two adjacent blank mold members and from which air is supplied at substantially uniform pressure to upper ends of cooling passages extending axially through the two blank mold members. This arrangement has been successful in operation, particularly because the uniformity of the pressure of the air supplied to the axial cooling passages enables calculation of the cooling effect of the air, but as one plenum chamber supplies one mold member of each blank mold it is not possible to differentiate between the cooling of the two molds.
U.S. Pat. No. 4,388,099 describes an arrangement for cooling the blank mold members at the blank station of a double gob IS machine in which air is supplied through a series of throttle valves to a number of chambers each arranged to supply air to some of a number of cranked cooling passages which extend partially obliquely and partially axially through the two blank mold members. The cooling effect of the air in this arrangement is not readily calculable not only because adjustment of the throttle valves alters the air flow unpredictably, but also because air flow in such cranked passages is also irregular, and the success of the cooling system depends on ad hoc adjustments of the various throttle valves.